Microinverters Are Launching a Solar Renewable Revolution
- Sunday, 01 May 2011
Given that solar-photovoltaic (PV) generating technology has been around for decades, one might think its general application in commercial and consumer circles might be a little more pervasive. After all, it is clean, safe, and relatively simple. Ask any expert and it’s likely you’ll get a litany of reasons why it has not gained more general acceptance — implementation costs, tricky installation aspects, long ROI, performance, and reliability are just a few. Fortunately, there is a game-changing technology — microinverters — that is ready to push solar PV’s acceptance and application past many of the current barriers.
Inversion Technologies 101
Solar-PV modules produce DC electricity, which typically needs to be inverted to AC before use. The traditional method to invert this power involves string inverter systems, which combine the energy from the various modules in an array on the DC side of the inverter, and invert them to DC all at once.
Microinverter systems for solar-PV inversion move the inversion capacity from a single inverter to multiple smaller inverters, immediately located to each PV module. These are connected in parallel on the AC side of the inverter, and connected to the utility system to create a grid tied system. The technological benefits and applications for this product make it an attractive choice for PV inversion.
As required by electrical code, microinverter systems on the market today include utility interactive phasing and anti-islanding technologies. Utility interactive phasing allows inverters to properly sync with the utility power that is present. This is accomplished by “pinging” the utility power with a waveform slightly different from the utility waveform and measuring the “push” that is received back from utility power. If no utility power is detected, these systems will automatically disconnect AC power production, a process known as anti-islanding. This is to protect utility workers who would be under the impression that no power is present when the utility system is down.
Microinverter installations offer users many benefits, including increased energy output, improved electrical safety, ease of system design and installation, and more precise monitoring capabilities. This is not the case with string inverted systems. With a typical string inversion system, every module in a string is limited by the weakest-performing module. For example, if a single module is partially shaded and loses 50% of its output, every module on that string becomes limited to the same 50% output.
More Power, More Safety
In a microinversion system, each module becomes an independent power-producing unit, and if one module is reduced to 50%, the other modules are not affected. Because the balance of the string is still producing at full capacity, more energy is harvested from the same modules when using microinverters.
Microinverters offer improved safety as a result of the reduction of the scale in the DC side of the system. Most installers are more familiar with AC wiring and AC arcing and grounding conditions, which are less dangerous and easier to isolate and control than DC arcing and grounding conditions. In a microinverter installation, the amount of DC wiring in the system is reduced to virtually zero.
Because there is no interaction between modules, installers are not required to balance systems. That means system designers and installers can use whatever roofs face the Sun at any given time (or Sun position) and be less concerned with the angles, and do not have to design around shading issues. While any of these will affect the performance of an individual module, a microinverter system as a whole can create usable power in layouts that a string inverted system would struggle to match in size and complexity.